Several studies have described the presence of the T2-FLAIR mismatch sign, characterized by hyperintense signal on T2-weighted sequences and hypointense signal on FLAIR sequences with a hyperintense peripheral rim, as a reliable and highly specific marker of IDH-mutant and 1p19q intact gliomas (astrocytomas).40–43Figure 3. The gene discussed is IDH1; the disease is astrocytoma (excluding glioblastoma).